1. Field of the Invention
The invention relates to methods and devices for supporting and holding open a tubular structure in the body of an animal or human. In particular, the invention relates to a stent that can be repositioned or removed once deployed.
2. Description of the Related Art
A stent is a device that can be placed within a body lumen for supporting and holding open a tubular structure in the body of an animal or human. In one common application, a stent is used for holding open a blood vessel. However, a stent can be used inside the lumen of any physiological conduit including arteries, veins, vessels, the biliary tree, the urinary tract, the alimentary tract, the tracheal bronchial tree, the genitourinary system, and the cerebral aqueduct.
Stents are generally tubular in structure and are radially expandable between an unexpanded insertion diameter and an expanded implantation diameter which is greater than the unexpanded insertion diameter. A stent is passed through the tubular structure in the body when collapsed, and then the stent will expand or can be expanded to its expanded implantation diameter after the implantation location has been reached.
Stents are generally categorized as being self-expanding, i.e., the stent expands by itself, or balloon expandable, i.e., the stent is expanded by a balloon inserted inside the stent. In one method for deploying a self-expanding stent, the stent is restrained within a sheath. After positioning of the self-expanding stent and sheath at the desired location in the lumen, the physician retracts the sheath to expose the stent and allow the stent to self-expand. In one method for deploying a balloon expandable stent, a delivery catheter assembly with an expandable balloon is used to deliver the stent. The stent is mounted on the balloon and the catheter assembly is pushed into the implantation site. Then, the balloon is inflated, radially applying a force inside the stent, and the stent is expanded to its expanded implantation diameter.
One problem with known stents is that they can be difficult to reposition or remove once deployed. Once a conventional stent is positioned in a particular tubular structure in the body and expanded in place, the stent cannot be reduced in diameter for repositioning or removal.
Thus, there exists a need for an improved stent that has an adjustable outside diameter such that the stent can be repositioned in, or removed from, a tubular structure in the body.